Using microarrays carrying 5, 569 cDNAs as well as several hundred previously defined Dictyostelium genes, we can examine the expression patterns of almost all developmental genes throughout the 24 hour cycle. Genes will be clustered on the basis of the time and cell type in which they are active and used to define developmental stages as well as give insight into physiologically significant differentiations. The synchrony of development in this system is such we have statistically significant 2 hour temporal resolution. The genetic networks that coordinate and modulate cellular functions during development can be further defined by microarray analyses of strains carrying null mutations in specific developmental genes. The relative developmental roles of internal cAMP and the cAMP dependent protein kinase PKA will be determined by microarray analyses of strains lacking one or more of the genes responsible for accumulation of response to cAMP. We have 4 general aims: 1) Detailed developmental patterns of gene expression will be established for strains NC44 and AX4 with microarrays carrying the full set of targets. Genes will be clustered on the basis of their cell-type specificity and expression profiles. 2) Microarray expression analyses will be carried out on strains with altered PKA regulation including those with mutations affecting adenyly cyclases, cAMP phosphodiesterases, cAMP receptors, PKA and modulators of these components. Several of these mutations affect the rate of development. Their temporal consequences to expression profiles will add another dimension to clustering. 3) The full developmental roles of the transcription factors MybB, GBF, STAT1, and MybC will be assessed by comparing cluster profiles in mutant strains lacking these factors to those in wild type strains. 4)The effects of null mutations in various specific developmental genes on the expression of clusters of genes will be used to construct networks of causal events that may account for temporal and cell-type specific differentiations in this system. Predictions derived from such networks will be tested when microarray analyses are extended to include further developmental mutants.